Electric radiator, modulating with downdraft compensation (RadEl11)

The figure below shows BACnet objects associated with this application function. Primary signal flow is summarized as follows:

Basic function: Accept request signal from associated room controller and pass it through a device mode logic switch; Output the result as a command to the BACnet object that controls the device.

Note
This AF does not perform loop control; its main purpose is to run commands. Loop control processes (for this AF) are managed in the "room" AF(s) that collaborate with this AF to command the end device.

Multiple radiator control: The radiator electric position collection object (RadElPosCol) can reference and control multiple radiators.

Radiator electric position objects (RadElPos) are referenced by the radiator electric position collection object (RadElPosCol); this collection object is a common node for any / all RadElPos object(s). The value for RadElPos comes from RadElPosVal.

Downdraft compensation: The downdraft compensation feature slows the sinking cold air flow at large window surfaces and combats cold wall effect at cold perimeter surfaces. This feature activates the radiator when the outside air temperature drops below a configured value, raising the minimum temperature of the radiator to a value higher than it would be otherwise.

Downdraft compensation is implemented using a linear reset function. The following graphic shows factory default values for X,Y downdraft compensation parameters.

Device mode: The input signal for device mode is a multistate value.

• Off
• Control mode (modulation)
• Fully open
• Ctrl.mode & downdraft (modulation plus downdraft compensation)
• Downdraft (downdraft compensation)

Heating available status: When the radiator(s) are available for heating, the binary output signal for "Radiator available for heating" (RadAvlH) will be "Yes" (available). RadAvlH is used by the system to regulate heating resources. For example, if there is a call for heating but the radiator(s) are not available because they are already at maximum capacity (because device mode is fully open), then RadAvlH will signal "No" and the next available heating resource in the temperature control sequence will be activated.

For heating available status to be "Yes", device mode must equal "Control mode" (modulation).

High temperature cut-out switch: This AF has a radiator over-temperature detection input (RadOvrTDet) from a high temperature cut-out switch. The over-temperature detection input object(s) are referenced by the radiator over-temperature detection collection object (RadOvrTDetCol); this collection object is a common node for any/all RadOvrTDet input object(s).

The RadOvrTDet objects are analyzed using an OR statement. If one or more objects detect over temperature, the binary result object (RadOvrTDetRs) switches from 0 to 1, causing the radiator to shut off at equipment protection priority.

Interface

Engineering and commissioning

If one high temperature safety switch trips, all the radiators driven by this AF shut down. Confirm function of safety switch for multiple radiators (multiple in and multiple out).

Design engineer may choose the type of output to the radiator(s). The logic to create each output type is embedded in the controller. There are two types of output:

• PID loop creates 0 to 100% analog heating demand signal to drive the electric radiator(s)
• PID loop creates 0 / 50 / 100% staged signal to drive the electric radiator(s)